1. Field of the Invention
The present invention relates to an apparatus for continuously dosing a patient with a liquid medicine at a moderate rate, by feeding it into a vein, urinary cyst or like organ. More particularly, the present invention relates to an apparatus that comprises a balloon accommodating a compressed amount of a liquid medicine to be supplied to a patient at a constant and moderate rate and in a continuous manner.
2. Prior Art
A device of a certain type for continuously dosing a patient with an antibiotic, anti-cancer medicine or the like is disclosed in Japanese Unexamined) Patent Publication Sho. 50-108970. This device comprises an elastic balloon which holds the medicine and tends to shrink to squeeze it into the patient's body. A bladder for a liquid medicine dispenser is proposed in Japanese Patent Publication Sho. 59-48881. The bladder is made of a synthetic polyisoprene. One of the present inventors a few years ago proposed an improved balloon for use in a device to continuously and constantly exert pressure on a liquid medicine. This balloon is a length of natural rubber tube having its inner surface coated with a silicone resin membrane, and has a composite structure in cross section as shown in Japanese Unexamined Patent Publication Hei. 4-2360.
Since the prior art balloons are cylinders having either or both ends closed, it has been difficult to manufacture a balloon having a peripheral wall of uniform thickness. Cylindrical balloons of an uneven wall thickness are likely to assume an irregular shape when inflated with a liquid medicine, due to an uneven distribution of stress. Consequently the flow rate of liquid medicine effluent through an outlet of the balloons has been observed to vary in the course of time. This in turn causes a fluctuation in pressure at an inlet of a flow regulator and a failure to dose the medicine at a constant rate to a patient and, thus, a failure to meet a requirement of the present invention.